212 COSMOS. 



the meteors move — can not at present be determined wrtn 

 certainty from the observations. A beautiful series of such 

 observations by Houzeau (during the years 1839 to 1842) 

 appears to offer evidence against a progressive alteration.* 

 Edward Heisf has very correctly remarked that, in Grecian 

 and Roman antiquity, attention had already been directed to 

 a certain temporary uniformity in the direction of shooting 

 stars darting across the sky. That direction was then con- 

 sidered as the result of a wind already blowing in the higher 

 regions of the atmosphere, and predicted to the sailors an ap- 

 proaching current of air descending thence into the lower re- 

 gions. 



If the periodic streams of shooting stars are distinguished 

 from the sporadic by the frequent parallelism of their paths, 

 proceeding from one or more points of divergence, a second 

 criterion of them is the numerical — the number of individua. 

 meteors referred to a definite measure of time. We come 

 here to the much-disputed question of the distinction of an 

 extraordinary from an ordinary fall of shooting stars. Two 

 excellent observers, Olbers and duetelet, have given as the 

 mean number of meteors which can be reckoned hourly in 

 the range of vision of one person upon not extraordinary 

 days, the former five to six, the latter eight meteors4 For 

 the discussion of this question, which is as important as the 

 determination of the laws of motion of shooting stars, in ref- 

 erence to their direction, a great number of observations are 

 required. I have therefore referred with confidence to the 

 already-mentioned observer, Herrn Julius Schmidt at Bonn, 

 who, long accustomed to astronomical accuracy, takes up 

 with his peculiar energy the whole phenomena of meteors — 

 of which the formation of aerolites and their fall to the Earth 

 appear to him merely a special phase, the rarest, and there- 

 fore not the most important. The following are the principal 

 results of the communications which I requested from him.§ 



* Saigey, p. 151 ; and upon Erman's determination of the points of con- 

 vergence diametrically opposed to the points of divergence, p. 125-129. 



t Heis, Period. Sternschn., p. 6. (Compare also Anstot., Problem., 

 xxvi., 23; Seneca, Nat. Qucest., lib. i., 14: " Ventum significat stella- 

 rum discurrentium lapsus, et quidem ab ea parte qua erumpit.") I 

 have myself long believed in the influence of the wind upon the direc- 

 tion of the shooting stars, especially during my stay at Marseilles at the 

 time of the Egyptian expedition. J Cosmos, vol. i., p. 113. 



$ All that is marked in the text with inverted commas I am indebted 

 for to the friendly communication of Herrn Julius Schmidt, attached to 

 the observatory at Bonn. 

 BPe Saigey, p. 159. 



